Singlet peak

As an example, an NMR spectrum of a 1,3-dioxolane-/3-propiolactone copolymer, obtained by using a boron-fluoride catalyst, is shown in Fig. 1101. The 1,3-dioxolane (DOL) homopolymer spectrum contains two singlet peaks of area 1 2 numbered 1 and 5, whereas the spectrum of the 0-propiolactone (PL) homopolymer contains two triplet peaks of area 1 1 numbered 2 and 6. Variation of initial feed ratios disclosed that peaks 1,3 and S are associated with the DOL units and that... 

It follows therefore that there is sufficient room around the metal atom to accommodate additional ligands. Also the displacement of the singlet peak on addition of increasing amounts of pyridine demonstrates that these... 

In H-NMR spectra, the acrylates showed a characteristic ABX pattern in the region of 8 6.8-6.0 with a pair of doublet couplings for each vinyl proton, while the methacrylates showed a characteristic AB pattern in the region of 8 6.5—5.8 with an equivalent singlet peak for each vinyl proton. The monomers purified by percolation over alumina contained no detectable hydrate water or polymerized impurities. 

Example Ethyl loss clearly predominates methyl loss in the El mass spectrum of 2-(l-methylpropyl)-phenol. It proceeds via benzylic bond cleavage, the products of which are detected as the base peak at m/z 121 and m/z 135 (3 %), respectively (Eig. 6.34a). The McLafferty rearrangement does not play a role, as the peak at m/z 122 (8.8 %) is completely due to the isotopic contribution to the peak at m/z 121. From the HR-El spectrum (Fig. 6.34b) the alternative pathway for the formation of a [M-29] peak, i.e., [M-CO-H]", can be excluded, because the measured accurate mass of this singlet peak indicates CgHgO". HR-MS data also reveal that the peak at m/z 107 corresponds to [M-CHs-CO]" and that the one at m/z 103 corresponds to [M-C2H5-H20]. Although perhaps unexpected, the loss of H2O from phenolic fragment ions is not unusual. 

The proton magnetic resonance spectrum (chloroform-d) of the pure product 2 showed a characteristic oxiranyl singlet peak at S 4.67 (singlet, 2H) and an aromatic signal at 7.2-7.8 (multiplet,... 

The following table lists the most popular reference standards used when NMR spectra of various nuclei are measured. The standards should be inert, soluble in a variety of solvents, and, preferably, produce one singlet peak that appears close to the lowest-frequency end of the chemical shift range. When NMR data are provided, it is always necessary to specify the reference standard employed.1-6... 

A symmetric Pt4 cluster in which all platinum atoms are chemically equivalent shows only one Pt NMR singlet peak. Table III summarizes the Pt NMR chemical shifts of symmetric Pt4 clusters. 

The singlet peak on the left comes from the -OH group, the triplet on the right from the-CH3 group, and the quadruplet from the -CH2 group. The small peak on the far right is the reference... 

N-terminal residue, while the second set of singlet peaks is formed by the protonated ions, which possess the C-terminal residues. Thus, each of these fragment ions could be analyzed in CAD mode with a triple quadrupole instrument (Fig. 72). 

The statistical theory also shows that the number of one-component or singlet peaks (an observed peak consisting of only one underlying component peak) Is given by... 

Since it Is the normal objective of chromatography to Isolate Individual coi ponents from all other components with a resolution of at least R the number of singlet peaks relative to the number of components m Is a measure of the success of separation. Unfortunately, Equation 10 shows that the s/m ratio falls off rapidly with Increase In saturation factor o. 

The singlet peak at 2.57 ppm in Fig. 8 was first assigned to both the methine protons attached to the MMA (MMA-H) and BIPK (BIPK-H) units located at the terminating chain end.59 Recently, the chemical shifts of MMA-H and BIPK-H were confirmed as 2.45 and 2.57 ppm for the poly(MMA-d8)s prepared with the initiators which did or did not give BIPK during polymerization.62... 

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